The Ocular Hypertension Treatment Study (OHTS) is a long-term randomized multicenter clinical trial to determine whether medical reduction of intraocular pressure prevents or delays the onset of glaucomatous optic nerve damage and/or visual field loss in ocular hypertensive subjects. 1,500 subjects with intraocular pressures of greater than or equal to 24 mm Hg but less than or equal to 32 mm Hg in at least one eye (with an intraocular pressure of 21 mm Hg or greater in the fellow eye), and normal visual fields and normal optic discs in both eyes are randomly assigned to receive stepped medical treatment to both eyes or to close observation only to both eyes. Participants are followed for a minimum of five years with conventional automated perimetry twice yearly and stereoscopic optic disc photographs once yearly. The study endpoints are reproducible optic nerve damage and/or reproducible glaucomatous visual field loss in either eye of a patient. Short Wavelength Automated Perimetry (SWAP) is a new visual field test procedure that isolates and measures the sensitivity of short wavelength (blue) sensitive visual mechanisms by projecting large (Size V) blue targets on a high luminance yellow background. Previous longitudinal studies conducted independently at the University of California, Davis and the University of California, San Diego have established that (l) SWAP is more sensitive than conventional automated perimetry for detection of early functional losses in glaucoma, (2) SWAP deficits in ocular hypertensive patients and glaucoma suspects are predictive of the onset and location of future glaucomatous visual field loss for conventional automated perimetry, (3) that the progression of SWAP deficits is approximately twice as great as for conventional automated perimetry, and (4) that early SWAP deficits in ocular hypertensive patients and glaucoma suspects are correlated with other risk factors associated with the development of glaucoma, especially glaucomatous optic disc cupping. This proposal describes an ancillary study to the OHTS trial that is to be performed at five of the participating OHTS Clinical Centers, in which participants will undergo SWAP testing. The main objective of this study is to determine the effect of treatment versus no treatment on SWAP results in ocular hypertensive patients. in particular, this investigation will examine the influence of treatment on reversibility of early SWAP deficits, determine whether progression of SWAP deficits is retarded by treatment, and whether the incidence of new SWAP deficits during the OHTS trial are reduced by treatment. A secondary goal of this study is to confirm previous findings that SWAP can predict the onset and location of future glaucomatous visual field loss, and that progression of SWAP deficits is more than twice as rapid as progression of visual field loss with conventional automated perimetry. Additionally, the prevalence and incidence of SWAP deficits in African American patients participating in OHTS will be evaluated to determine whether African-American ocular hypertensives have a higher prevalence and/or incidence of SWAP deficits.